Apparatus for checking the integrity of electric circuits



July 29, 1952 c. M. HINES APPARATUS FOR CHECKING THE INTEGRITY 0FELECTRIC CIRCUITS 2 SHEETS-SHEET 1 Filed May 5, 1948 wow CuNJ

O T mOT lNVi NTbR. CLAUDE M. HINES QZJJZZO ATTORNEY July 29, 1952 c MHINES 2,605,329

APPARATUS FoR'CHCKINC THE INTEGRITY OF ELECTRIC CIRCUITS Filed May 5.1948 2 SHEETSSHEET 2 FIG! INVENTOR. CLAUDE M. HINES ATTORNEY PatentedJuly 29, 1952 APPARATUS FOR CHECKING THE INTEGRITY OF ELECTRIC CIRCUITSClaude M. Hines, Verona, Pa.,"assignor to Westinghouse Air BrakeCompany, ,a corporation of g Pennsylvania Application Ms 1948, SerialNo. 25,208

14 Claims. 1

This invention relates to a circuit checking means, and moreparticularly, to an apparatus adapted to be associated with train wirecontrol circuits of electro-pneumatic brake systems on railway trainsfor automatically signalling the integrity or lack of integrity ofthetrain wire circuits and windings .of electrical devices associatedtherewith. Most high speed trains of todayare equippe with a combinationof two brake control systems, .either of which is alternately andindependently .operative of the other. Such brake controlequipmentsusually include an electropneumatically controlled straight-airbrakesystem and a wholly pneumatically controlled automatic brake system,each of which is controlled by a single control lever on a single brakecontrol valve device. A brake control apparatus of this type isillustrated and described in Patent No. 2,105,483 issued to E. E.Hewitt, January 25, 1938.

The automatic brake system. is characterized by a normally chargedcontrol pipe, commonly knownas the brake pipe, extending from one end ofthe train to the other with a branch pipe leading from the brake pipe toa brake control valve device on each car of the train. Selectedvariations of the fluid pressure in this brake pipe causes operation ofthe brake control valve device on each car to eifect either a brakeapplication or brake release as desired. The variation of fluid pressurein the brake pipe travels by wave action, at a speed somewhat less thanthat of sound in air, from the-point of origin, usually the locomotive,to all other parts of the train. This wave action is effective toproduce a serial action of the brake control valve units on the cars forsequentially applying or releasing the, brakes on successivecars of atrain. This serial brake action results in a sleek action between thecars of the train attended in some instances by shock to .the cars, andin'the case of passenger trains, discomfort to the passengers.

The electro-pneumatically controlled straightair brake control system,making use 'of electric current to control the brake. operation,producespractically simultaneous and uniform con trol of the brakes onall cars. The simultaneous and uniform action of the brakes as a resultof instantaneous transmission of the electrical control impulsesthroughout the train, mini- 2 mizes the slack action between the carsand produces faster and heavier applications of the brakes, therebyenabling shorter stopping distances than may be obtained with theautomatic brake control system. I

For convenience, the electro-pneumatio straight-air brake control systemwill hereinafter he referred to as the straight-airbrake system and thewholly pneumatically controlled brake system will be referred to as theautomatic brake system.

Because of the advantages inherent in the straight-air brake system overthe automatic brake ssytem, the straight-air brake system is customarilyemployed in preference to the latter system. The'automatic brake systemthus serves as an alternate brake system to be used in most instances inthe event of failure or a faulty condition of the straight-air brakesystem. 1 I

The present straight air brake systems employ control wires or circuitswhich extend from the locomotive or control car at the head end of thetrain through all cars in the train, suitable electric couplers beingprovided between the cars for serially connecting each corresponding carwire into one continuous conductor through the train. By reason of theflying ballast and water, attendant upon a fast moving train, and thelost motion between the individual cars, theelectric couplers arevulnerable to faults, such as open circuits, shorted or groundedcircuits which may cause failure of the straight-airbrake system tofunction either partially or even-completely. If the nature and locationof the fault can be determined, it is possible to correct the faultycondition and thus restore'the straight-air brake system to its fullserviceability without-the loss of its utility.

The straight-air brake system usually includes two magnet valves,commonly referred to astheapplication magnet valve and the releasemagnet valve, on each car of the train. The release-magnet valves arefirst operated, upon the initiation of a brake application, to close anatmospheric port from a pipe extending from car to car and throughoutthe train and commonly known as the straight-air pipe. The applicationmagnet valves are next operated to source, to' astraight-air pipe. Theuniform fiuid pressure thus established throughout the length of thestraight-air pipe controls, either directly or indirectly, the fluidpressure established in the brake cylinders on all cars in the train andthereby causes a uniform degree of brake application to besimultaneously effected on all cars.

A failure of a small percentage of the application magnet valves tosupply fluid under pressure to the straight-air pipe during astraightair application of the brakes, reduces the rate of build-up ofbraking forces. but does not alter the degree of the application for thereason that the straight-air pipe is continuous and the operativeapplication magnet valves are effective to establish the properstraight-air pipe pressure.

The failure of a small percentage of the release magnet valves tooperate during a straight-air brake application to close theirindividual exhaust communications from the straight-air pipe to theatmosphere, is a matter of grave concern. In such cases, not only is therate of development of the application retarded, but also the degree ofapplication attainable is lowered and the available fluid under pressurefrom the source of supply, vital to the safe operation of the brakeequipment, is concurrently released to the atmosphere. It is thusessential that the operator be made promptly aware of the faultycondition of the electro-pneurnatic brake control equipment in order toavoid loss of fluid pressure supply. For safety reasons also it isundesirable to lose the time necessary to determine a faulty straightairbrake equipment by attempting a straight-air application beforeresorting to the automatic brake system.

The desirability of continuously indicating the integrity or lack ofintegrity of the electrical control circuits and of the magnet valvewindings in the electro-pneumatic brake control systems has beenpreviously recognized and several means and methods have been proposedand employed for this purpoe. I propose, however, to provide a novelapparatus, capable of detecting faults in the electrical controlcircuits, or in the windings of magnet valves associated therewith, insuch a manner as to indicate not only the nature but also the locationof any fault in the system.

It is accordingly an object of my invention to provide a novel apparatusfor reliably indicating and signalling the integrity, or lack ofintegrity, of electrical control circuits.

A further object of my invention is to provide an apparatus, constructedon the Wheatstone bridge principle, adapted for use in conjunction withelectro-pneumatic brake control systems of the type employed in railwaytrain service, in a manner to identify which of a plurality of controlcircuits is faulty and also to indicate the nature and location of thefault.

Still another object of my invention is to provide an apparatus forchecking the condition of electrical control circuits, which system isautomatically disconnected from the control circuit at the time of acontrol operation to avoid interference by the checking system with thecontrol operation and then automatically restored to function with thecontrol circuit as soon as the control operation is completed.

Another object of my invention is to provide a circuit checkingapparatus constructed in a compact portable form such that it may beconveniently installed and applied without difficulty to anelectro-pneumatic train brake control system or to any other similarelectrical control 4 circuits for the purpose of checking the integrityor lack of integrity of the circuits.

Yet another object of my invention is to govide a circuit checkingapparatus of the type indicated in the foregoing objects furthercharacterized in that an application of the brakes by the automaticbrake system is effected without delay, should the operator attempt astraight-air brake application when or while the control circuits areindicated as faulty.

The above objects, together with other objects which will be madeapparent in the subsequent description of my invention, are attained byapparatus to be herinafter described when read in connection with theaccompanying drawings, wherein Figs. 1 and 2, when taken together,constitute a diagrammatic view showing a simplified brake controlequipment for railway cars and trains embodying my novel circuitchecking and signalling system.

While a simplified brake control equipment is shown in the drawings forthe purpose of illus trating the nature and utility of my novel circuitchecking system, it will be understood that the apparatus illustratedand described herein may be applied to and function with various othertypes of control circuits.

The brake control equipment shown in Fig. 1 is that required for thelocomotive or traction vehicle of a train, and may include a brake valveI, an equalizing discharge valve device 2, a vent valve device 3, amagnet valve device 4, a master switch device 5, an application andrelease magnet valve device 6, an automatic brake control device 1 and abrake cylinder 8.

The brake valve device I is preferably the same as, or similar to, thatdescribed in Patent No. 2,106,483 to E. E. Hewitt, dated January 25,1938. It is not essential to the understanding of the present inventionthat this brake valve device be either fully shown or described indetail, and for that reason, I have elected to refer only to thosefunctions of the brake valve device essential to an understanding of theoperation of the brake equipment illustrated.

The brake valve device I is preferably operated by movement of a handle9, in a single application zone, to control all applications of thebrake. In order to accomplish this, the brake valve is provided with aselector II], which in one of its two positions, conditions the brakevalve for straight-air brake operation, and which, in the other of itstwo positions, conditions the brake valve for automatic brake operation.

When the selector Iii is in the straight-air position, and the handle 9is in release position, the straight-air control pipe I I is incommunication with the atmosphere, while the brake pipe 12 is beingmaintained charged from the main reservoir 13, under the control of afeed valve I4, by way of a feed valve pipe I 5 and a branch pipe 16. Astraight-air application of the brakes is effected by moving the handle9 to any desired position into the application zone, whereuponcommunication between the control pipe II and the atmosphere is closed,and fluid under pressure is supplied to this control pipe to a degreedependent upon the degree of movement of the handle 9 into theapplication zone. During this movement of the handle 9, the brake pipeI2 continues to be maintained charged from the main reservoir I3 to theadjusted setting of the feed valve l4.

When the selector 0 is in the automatic position, and the handle 9 is inthe release position, the straight-air control pipe II will be connectedto-theatmosphere and -the ;brake pipe will be charged as beforedescribed. When it is desired to efiect an automatic application of thebrakes, theha-ndl'e 9 is first moved to a first service, or slackgathering position, in the case 'oflong trains, and then to full serviceposition. If the train is short in length the brake valve handle may bemoved :to thefull service position in'the first instance. In the firstservice position of the brake valve handle a slow "rate of reduction ofbrake pipe pressure results and in the full service position brake pipepressure. willcontinue to be reduced at a service rate until the handleis returned to the lap position. The degree of reduction in thebrakepipe pressure is thus controlled according to the duration of time inwhich the handle 9 remains in the full, service position. During thismanipulation of the handle,- the straigliteair control pipe H willcontinue to be connected to the atmosphere.

Regardless of what position the selector H! is in, if the handle 9 isturned to an emergency position, the brake pipe l2 will be vented to'theatmosphere directly, by the operation of a se'pa rate valve devicewithinthe brake valve.

The-functioning of the brake valve i. will be more fully understood fromthe description-oi the equipment operation which will followhereinafter.

i The equalizing discharge valve device 2 is'e'mbodied in a casingcontaining a piston H subject on its upper side to the pressure of fluidin a chamber 18 and on its lower side to the pressure of fluid in achamber). Attached to the piston I1 is a stem 20 having one end thereofslidable in a bore H. The stem 2c is recessed at 22 to receive the endof a lever '23. The lever23 is pivotally mounted as on a pin 24 attachedto the'casing and has an extension 25 for operating a vent valve 28. Thevent valve'26 is normally biased to a seated position by a spring 21,but upon counter-clockwise movement of the lever 23 about pin 24, thevent valve 26 is unseated to open the communication between the chamberI9 and anequalizing discharge passage 28 leading to the brake valvedevice. The chamber [3 is connected by a pipe 29 to the brake valvedevice I and to an equalizing reservoir 39 by a branch of pipe 29.

Operation of the equalizing discharge valve device is eilected byreducing the pressure of fluid in chamber l8 and in the equalizingreservoir, whereupon the piston I? will be shifted upwardly due to theunbalancing of fluid pressures in the chambers IS and Id. The upwardmovement of the piston ll rotates the lever 23 in a counterclockwisedirection about the pin 24 to unseat the vent valve 26. will appear moreclearly hereinafter, unseating of the vent valve 25 allows fluid underpressure in chamber is to flow to theatmosphere until the pressuretherein becomes slightly less than the pressure in chamber l8'-'and theequalizing reservoir 39, whereupon the pisto'n ll will be returned bythe unbalanced fluid pressures to the position shown wherein the ventvalve 26 is seated by its spring 21. Since the chamber is is connectedto the brake pipe by way-of a branch pipe lib pipe 3i and vent valvedevice 3 as more fully described presently, it follows that anyreduction of pressure in chamber I?! will effect a correspondingreduction of the pressure in the brake pipe and that the brake pipepressure reduction can be controlled inaccordance withthe degree ofreduction; ofthe pressure in the equalizing reservoir and'in cham-.

ber"l-8.- I The. vent valve devices comprises a casing containing apiston 32, subject on the one side tothe combinedrpressure of fluid in achamber 33 which is in continuous communication with pipe 39, and thatof a springi d, andisubjecti'on the other side to the pressure of fluidin a chamber 35, connected-at all times to the branch pipe 16.. 'Arestricted: port 36 in the piston-3'2 permits the .fluid pressure inchamber 33 to normally equalize into chamber 35 so that the spring 34iseffective to shift the piston 32 to its lower, or normaltpositionqAttached to the piston 32 is a valve 3'? which is held on a seat rib 38by the force of the spring 84 when the pressure in the two chambers 33and 35 are equalized.

In thelower-most position of the piston 32,-=a communication isestablished between the brake pipe I2 and the pipe'l'G leadingto thebrake valve. The chamber 34 above the piston 32-i-s connected by a pipe39 to thebralrevalve device l and by branch pipe to theinag-net valvedevice 4. Upon the release of pressure in the pipe ss' 'and in thechamber 3 4, the over-balancing pressi :e'in the chambered-wills'hiftthe piston 32 to its upper position, wherein the communicationbetween the pipe 6 and brake pipe I2 is cut oil and the brake pipe 42 isconnected pastthe valve 3 1' and the seat rib 38 to the atmospherethrough large port 30. This rapid-1y reduces the brake pipe pressure, tocause an emergency application of the brakes, as will hereinafter bedescribed.

-'I he magnet valve device 4 is "embodied 'in'a casing having therein-valve 41 which is urged toward an unseatedposition by a spring-42 andactuated to a seated position upon energization of an electro-magnetWhen the "electro magnet-43 is deenergized the spring "42 'unseats valveii to "establish acommunication between the'branch-of pipe 35) andthe'atmosphere through a port M. As long as the 'electro-"1nagnet43 isenergized, the valve "4'! is heldto its-seat 'and' lthe communicationbetween the pipe 38 Land the atmosphere through port is closed.

The master switch device s comprises a casing containing two flexible'diaphragms 45 and 46, disposed therein in spaced coaxial relationshipand connected by a stem 41. At the outer side ofthe diaphragm-45 is achamber "48 connected to the straight-air control pipe I I. On the outerside of diaphragm 46 is a chamber 49 that is connected to a straight-airpipe 50. The two diaphragms '45 and 46 and'the casing define a chamber5| through which the stem 47 extends.

Two movable'contact 'memb'ersf52 and 53 are disposed in chamber SI andrigidly securedlto the stem 41' by an insulation spool '54, the contact,member 52 being known as the release contact member and the contactmember 53 being known as the application contact member. Both contactmembers are adapted to move with movement of the stem 41 from theposition shown toward the right, that is, in the direction of chamber49, to first efiect an engagement of the release contact member 52 with.a pair of resilient contact members 55 and 55. A further movement ofthe stem will effectan engagement of the application contact member witha pair of resilient contactmembers '51 and 5a. The resilient contactmembers 55, 5s, 51 and 53 are springsupported and will yield underpressure to permit continued movement of the insulation spool and thecontact members 52 and 53 after engagement with the resilient contactmembers. The resilient contact members 55 and 58 are connected to a wire59 connected to the positive terminal of a supply battery 60 by a supplywire 6 I. The resilient contact mem ber 56 is connected to a releasecontrol wire 63, hereinafter referred to as the release wire, andengagement of the contact members 55 and 58 by the contact member 52results in energization of the release wire. The resilient contactmember 5! is connected to an application control wire 52, hereinafterreferred to as the application wire, and engagement of the contactmembers 51 and 58 by the application contact member 53 results inenergization of the application wire 62.

Contained in the chamber 49 is a springsupported stop member 64 which isengaged by the stem 41 at a point in the travel of the stem in which therelease contact member 52 engages contact members '55 and 56 and beforeengagement of the application contact members 5'! and 58 by contactmember 53. This spring stop serves to stabilize the switch deviceagainst any tendency to a pumping action and to define a so-called lapposition thereof.

The application and release magnet valve device 6 comprises a casingcontaining a supply valve 65 normally urged into seated position by aspring 85 and actuated to an unseated position by energization of awinding 61 of an electro-magnet. The supply valve 65 is located in achamber connected to the feed valve pipe 15 by a branch pipe 68. Whenunseated, the supply valve 85 will permit the flow of fluid underpressure from the branch pipe 68, past the valve 65, to a chamber 69 towhich the straight-air pipe 50 is connected. Also disposed in the magnetvalve device casing is a release valve 10 which is normally urged to anunseated position by a spring H to connect the straightair pipe 50 tothe atmosphere via a port 13 and actuated into a seated position byenergization of a winding 12 of an electro-magnet.

One terminal of the winding 61 is connected by a branch wire 62a to theapplication wire 82 which extends through the train. The other terminalis connected by a branch wire 15a. to abattery return wire 15 connectedto the negative terminal of the supply battery 60.

One terminal of the winding 12 is connected by 'a branch wire 63a to therelease control wire 63 which extends through the train and the otherterminal is connected by the branch wire 15a to the battery return wire15. Energization of the application and release windings 61 and I2 isthus controlled by the master switch device '5 as will be hereinafterexplained.

The automatic brake control device 1 comprises a casing having therein apiston 74, subject on one side to the pressure of fluid in a chamber 16,and on the other side to the pressure of fluid in a chamber TI. Thepiston 14 is provided with a stem 18, which is recessed to receive, andto move with movement of the piston, a graduating slide valve 19.. Thestem 18 is further provided with collars and 8| so spaced as to engage amain slide va1ve.82 therebetween with a certain lost motion.

The chamber 76 is connected by a branch pipe 83 to the brake pipe 12.The chamber 11, in which is located the stem 18 and the slide valve 82,is connected by a branch pipe 84 to the auxiliary reservoir 85. Theparts of this automatic brake control device brake are illustrated inwhat is known as the brake release position,

in which the auxiliary reservoir '85 and the slide valve chamber 1! arecharged from the brake pipe I2 by way of the branch pipe 83, chamber 16and a feed groove 86, which in this position of the piston 14 connectsthe chambers 16 and 11. In this release position of the slide valve 82,a cavity in the slide valve connects a passage and pipe 87 leading to adouble check valve 88, and to the brake cylinder 8 during an automaticbrake application, to an atmospheric port 89 for the release of fluidpressure in the pipe 81 and the brake cylinder.

With the brake pipe and the auxiliary reservoir charged with fluid underpressure, a reduction of the brake pipe pressure at a rate suflicient tocreate the necessary differential pressure across the piston 14 causesthe piston to be shifted to the left. The initial movement of the pistonand the graduating valve 19 uncovers a service port 98 in the main slidevalve 82, the piston simultaneously closing the feed groove 88, cuttingoff communication between the chambers l6 and 11. The continued movementof the piston 14 by reason of the brake pipe reduction causes the collar8| on the piston stem to engage the slide valve 82 and move it to aposition in which the service port 90 registers with the port and pipe81. Communication is thus established through which fluid under pressureis supplied from the auxiliary reservoir past the valve element of thedouble check valve 88 to the brake cylinder 8 to establish fluidpressure therein, resulting in an application of the brakes. As theauxiliary reservoir pressure is reduced by flow of fluid under pressuretherefrom to the brake cylinder, in effecting the brake application, theunbalance of forces in effect across the piston 14 is diminished andwhen the auxiliary reservoir pressure is reduced slightly below thepressure in the brake pipe and connected chamber 16, the piston and thegraduating valve will be moved in the right-hand direction to aso-called lap position in which the graduating valve 18 covers theservice port and cuts off further supply of fluid under pressure throughthe communication between the auxiliary reservoir and the brakecylinder.

When fluid under pressure is again supplied to the brake pipe [2 forrestoring the pressure therein, as will hereinafter be described, thepredominating force of brake pipe pressure over the auxiliary reservoirpressure will cause the piston H to move the main slide valve into therelease position, in which it is shown, again connecting the brakecylinder to the atmospheric port 89 and opening the feed groove 86 topermit a recharge of the auxiliary reservoir.

The equipment just described is a simplified combined automatic andstraight-air brake control equipment such as may be applied to thelocomotive. For simplicity the brake control apparatus for the cars isnot shown in the drawings but it should be understood that the equipmenton each car may include an application and release valve device 6, anautomatic brake control device I, an auxiliary reservoir 85 and a brakecylinder 8. The application and release valve device 7 on each car isconnected by a pipe to receive its supply of fluid pressure from theauxiliary reservoir on the respective car or from a separate supplyreservoir charged from the brake pipe. The electro-magnet windings 61and 12 on the cars are connected in a manner similar to that shown forthe locomotive, namely to the application wire 62, release wire 63 andbattery return wire I5 which extend from the'locomotive through each carto the last car of the train. The respective application and releasemagnet valves on the locomotive and all cars of the train are thuscontrolled simultaneously by selective control of energization of theapplication and release wires.

Assuming that the main reservoir I3 is charged with fluid underpressure, and that the selector I is in the straight-air operationposition, the apparatus thus far described will operate as follows:

With the brake valve handle 9 in the release position, the fluid fromthe main reservoir I3 will flow, at a certain pressure regulated by thefeed valve I4, to the pipe I5, then through the rotary valve of thebrake valve I, to the pipe. I6 leading to the vent valve device 3 and tothe brake pipe I2. Fluid under pressure in brake pipe I2 flows by way ofthe branch pipe 83 to enter chamber I6 on the face of the piston H ofthe automatic brake control device I on the 1000- motive and similardevices on each of the cars in the train. With no pressure in theauxiliary reservoir, brake pipe pressure in chamber 16 will force thepiston I4 to the position in which it is shown wherein the feed groove86 is opened to allow communication fromethe chamber II; to. the chamber11 and to the auxiliary reservoir 85. After suflicient time theauxiliary reservoir 85 on the locomotive and all cars of the train will.be charged to the brake pipe pressure as regulated by the feed valve I4.At this same time, fluid under pressure as regulated by the feed valve I4 is permitted toflow through a restricted port in the rotary valve ofthe brake valve to pipe 29 leading to the equalizing reservoir 30 and tochamber I8 above the equalizing piston I'I. With the brake pipepressure, active'in chamber I9 below the equalizing piston H, of equalvalue to the equalizing reservoir pressure in chamber I8, the Weight ofthe piston I! together with the force of spring 21 acting against theexhaust valve 26 will maintain the exhaust valve on its seat. In thisrelease position of the brake valve handle 9, the straight-air controlpipe II is connected through the self-lapping portion of the brake valveI to the atmosphere. The brake cylinder 8 on the locomotive and on eachcar in handle 9 is moved from the release position to ward the fullservice position to an extent according to the desired degree ofapplication of the brakes, that is, the degree of angular movement ofthe handle determines the degree of the brake application.

With the selector I9 in the straight-air operation position, theself-lapping portion of the brake valve device is operative to controlthe flow of fluid under pressure from the feed valve pipe I to pipe IIand to chamber 48 of the master switch device to a value proportional tothe degree of movement of the handle 9 in the direction of the fullservice position. Fluid under pressure in chamber 48 will operate theswitch portion, to in turn effect operation of the application andrelease magnet valve device 6, as before described, to establish apressure in the straight-air pipe 59' equal to thepressure in pipe IIand chamber 48.. Since the straight-air pipe is. connected by way of thedouble check valve 88 to the brake cylinder 8, it follows that fluidpressure will be established in the brake cylinders equal to thestraight-air pipe pressure.

The degree of the application may be increased by moving the brake valvehandle further toward the full. service position, and may be decreasedby moving the handle toward the release position. When it is desired toeffect a full release of the brakes, the brake valve handle is returnedto the release position, whereupon fluid supplied to pipe. II and tochamber 48 is released to the atmosphere by th self-lapping portion ofthe brake valve. Fluid pressure in the straight-air pipe 58 and hencethe brake cylinders is effective in chamber 49 to effect operation ofthe switch portion of the master switch device to control theapplication and release magnet valve devices to release the straight-airpipe and brake cylinder pressures to the atmosphere.

When. it is desired to effect an application of the brakes by automaticoperation, the selector I0 is' first moved to the automatic position.Then with the brake pipe and auxiliary reservoirs throughout the traincharged to the setting of the feed valve I4, as before described, thehandle 9 is moved from th release position through a lap position intothe service posi tion. In this service position of the'handle 9, therotary valve in the-brake valve disconnects the branch pipe. I6 and theequalizing reservoir pipe 29 from the feed valve pipe I5, and connectsthe equalizing discharge pipe to the atmosphericexhaust and fluidpressure in the equalizing reservoir to exhaust through a restrictedpassage. Fluid. under pressure in the equalizing reservoir 30 and inchamber I8 of the equalizing discharge valve device thus reduces to theatmosphere at a controlled rate during all the time the handle 9 is inthe service position. As soon as thedesired degree of reduction ofequalizing reservoir pressure is effected, the brake valve handle 9 isreturnedv manually to the lap position. The reduction in fluid pressurein chamber I8 results in an unbalance of pressures across piston I! withthe result the piston moves upwardly unseating valve 26 to reduce brakepipe pressure to the atmosphere until brake pipe pressure is reduced tothe reduced value of the equalizing reservoir pressure.

. When a reductionof brake pipe pressure is effected, a correspondingreduction of fluid pressure takes place in chamber 15 of the automaticbrake control devices 7 on the locomotive and each car of the train. Thepiston M is shifted to the service position so that fluid pressure fromthe auxiliary reservoir is connected through the slide valve port 90- tothe brake cylinder until auxiliary reservoir pressureis reduced to apressure corresponding to slightly less than-brake pipe pressur when thepiston moves to the lap position wherein the graduating valve I9 coverstheservice port 90 to cut on further flow of auxiliary reservoirpressure to the brake cylinder.

It will be obvious that the degree of the brake application iscontrolled according to the degree of reduction in theequalizingreservoir pressure and that a graduated control of the brakesis obtainable by proper manipulation of the brake valve handle.

To effect a release of the brakes following an automatic application,the brake valve handle 9 is returned to the release position in whichthe brake pipe pressure is restored from the main reservoir. Theincreasing brake pipe pressure is effective in the automatic brakecontrol device I to force the piston 14 to release position in which theauxiliary reservoir may be recharged and the brake cylinder pressure isconnected to the atmosphere.

An emergency application of the automatic brakes may be effectedmanually by movement of the brake valve handle to emergency position, inwhich position the rotary valve of the automatic brake valve ispositioned to connect the pipe I6 to the atmosphere through a largeopening, or b removal of the operators hand from the brake valve handlein the well-known manner of deadman control. In this latter instance,fluid pressure is released from pipe 39 and chamber 33 of the vent valvethrough the brake valve. Th piston 32 is unbalanced by reason of theloss of fluid pressure in chamber 33, and the piston 32 thus movesupwardly to out 01f communication from pipe It to brake pipe I2 and atthe same time connect brake pipe I2 to the atmosphere through the largeport 40 to effect reduction of the pressure therein at a rapid rate.

An emergency application of the automatic brakes may be further effectedautomatically by deenergizing the magnet valve device 4.

The magnet valve 4 is shown normally energized by a circuit from thesupply battery controlled by a speed responsive switch M and, as will beexplained later, by the circuit checking equipment constituting myinvention. Deenergization of the magnet valve 4 by any cause such asloss of supply current, operation of either the speed-controlled switchor the circuit checking equipment will result in the venting of fluidpressure from chamber 33 of the vent valve device 3 and in an emergencyventing of brake pipe pressure to the atmosphere.

Emergency venting of the brake pipe pressure results in brake pipepressure being quickly reduced to atmospheric pressure. Such a reductionin fluid pressure in chamber 16 of the automatic brake control device 1results in movement of the piston M to application position and inequalization of auxiliary reservoir pressure into the brake cylinderthus producing an application of the brakes with maximum force.

According to my invention, the circuit checking and signallingapparatus, which I propose to use in conjunction with the abovedescribed brake control equipment to indicate the operative condition ofthe brake control circuits and to eifect an automatic application of thebrakes should the operator attempt a straight-air brake application whenthe electrical control circuits are faulty, is shown in Fig. 2. Thiscircuit checking apparatus comprises essentially a Wheatstone bridgearrangement for each of the two brake control circuits to be checked. Itwill be recalled that the brake equipment just described employs twocontrol circuits, namely (1) the release control circuit comprising therelease control wire 63 and the return or ground wire 15 extendingthroughout the train with the windings 72 of the release magnet valve onthe locomotive and difierent cars in the train connected in paralleltherebetween and (2) the application control circuit comprising theapplication control wire 62 and the return or ground wire I5 with thewindings 67 of the application magnet valves on each of the dillerentcars in the train connected in parallel therebetween.

The circuit checking equipment comprises two '12 similar, Wheatstonebridge arrangements 92 and 93, thebridge arrangement 92 being applied tothe application. control circuit and the bridge arrangement 93 beingapplied to the releasecontrol circuit. These bridge arrangementstogether with the necessaryv cooperating relays and indicating signalsare included in a portable equipment case 94 with the necessary leadwires, as identified hereinafter, for connecting to the train wires, andto the signals, etc. Each bridge arrangement comprises the usual fourbranches, one of the branches including the control circuit to bechecked. Specifically, the Wheatstone bridge arrangement 92 includes asone branch thereof a fixed resistor 95, and a second branch including,in series, a fixed resistor 96 and a temperature compensating resistor91. The temperature compensating resistor may be located remotely. ofthe portable case 94 so as to be subject to the atmospheric temperatureand not influenced by locomotive cab or control car temperature wherethe checking equipment may be located. Automatic compensation forchanges in control circuit resistance due to atmospheric temperaturevariation is thus accomplished. The resistor 91 is. connected into thebridge branch by suitable leads 98 and 99 between the resistor andsuitable binding posts on the equipment case. A condenser I00 carriedwithin the case 94 is connected across the leads to said binding postsso as to parallel the resistor 97 and serves to prevent any inductiveeifect of current variations in the bridge .oircuit from influencing thebridge balance condition.

Another or third branch of the bridge arrangement 92 includes theapplication magnet control circuit. This branch includes wire IOI,resistor I02, switch contact member I03 of a relay I04, hereinafter tobe described, wire I05, binding post I06 on the case, lead 10.! to theapplication train wire 62, then over the various application magnetwindings 61, in parallel, to the battery return or ground wire 15, leadI08, binding post I09 on the case 94, iuse IIO, switch III, wires H2 andH3 to the junction H4.

The fourth branch of the bridge arrangement comprises wire II5,resistors H6 and Ill, Wire IIB, variable resistor or rheostat II9,having a manually operable contact arm I20, and wire I2I to the junctionH4. Operation of the contact arm I20 is arranged to effect operation ofa switch I22 to closed position, for a purpose hereafter explained, whenthe arm is positioned for more than a predetermined number, say five,cars ilrathe train as indicated on an escutcheon plate The first branchof the bridge 92, resistor 95, is joined to the resistor 96 of thesecond branch at a junction I24 and to the fourth branch at the junctionof wire II5 with the resistor. The second branch of the bridge is joinedto the third branch of the bridge by wire I25 and a back contact memberI26 of a relay [2! later to be described.

Operatively responsive to a balanced and an unbalanced condition of thebridge circuits and connected in series between wires H5 and I25 are adetector relay I28 and a meter I29. The meter I29 is normallyshort-circuited by a circuit including a wire I30, a normally closedswitch contact member I3I of a manually operable switch I32, hereinafterdescribed, and wires I33 and I 25 to remove the resistance of the meterfrom the relay circuit during the automatic operation of the bridgearrangement.

Further associated with the bridge 92 is a circuit including wire H3, anormally closed-switch contact member I34, of switch I32, wire I35, tocontact member I26 of a relay I21 and a contact member I36 of a relayI31 to be described later. This circuit, is arranged under certainconditions to alternately short-circuit first the third branch and thenthefourth branch-of the bridge to produce an intentional unbalancedcondition thereof.

The resistors I62 and H8 in the third and fourth branches of the bridgearrangement. are matched ballast resistors included in the'bridgecircuit to increase the potential across and in: sure operation of thedetector relay I28 when checking the control circuit of along trainwherein the resistance of the third and fourth branches is low.

The resistor Ill in the fourth branch of the bridge isv of a value equalto the resistance of the winding 61 of the application magnet on thelocomotive.- With the resistance of the locomotive brake controlequipment in the third branch of the bridge thus matched in the fourthbranch, the resistor H9 and contact arm I20 can be calibrated suchthatthe exact number of application control magnet windings in the trainbrake control equipment can be determined by adjusting the, contact armon the resistor until the bridge arrangement is in a balanced condition.

Two current limiting resistors I38. and I 33 are placed in series in thevoltagesupply circuit for the bridge arrangement. The resistor I38isomitted when the checking equipment is used on circuits of: the sameoperating voltage as that for which the equipment was designed and. isemployed when checking circuits operating on a highervoltage. Theresistance of the resistor i'38 is, thus determined by the voltageapplied tothe checking equipment in excess-of, that for which theequipment is designed. The resistor I39-is arranged to be cut by switchI22 when less than a given number of cars, say five, are included inthetrain to avoid possible undesired energization of. the. applicationcontrol circuit at that time and the. consequent undesired applicationof the brakes. The switch I22 is arranged to be automatically opened to.cut resistor;

[39 in bya cam on a. shaft, indicated by the broken line, supporting thearm I20 when the arm indicates less. than five cars.

The bridge arrangement 93 is substantially identical in construction tothe bridge arrangement Q2 and it is deemed unnecessary, therefore, todescribe bridge arrangement. 93 in detail as this may be understood fromthe previous description of bridge arrangement 92.

The reference numerals M to I15, inclusive. are thus applied withoutrepetitive description to identify the elements of the bridgearrangement 93, in consecutive order corresponding to application of thenumerals 95 to I 39 inclusive to the elements of bridge arrangement 92,except in cases where the elements are common to both, of the bridgearrangements. It will be understood, of course, that the third branch ofthe bridge arrangement 83 includes the release control circuit insteadof the application control circult.

A two-winding polarized relay I16 is associated with the relays I28,I66, I31 and I21 and cooperates with these relays to produce a codingoperation of a given frequency, when the two control circuits beingchecked retain their fide1- ity, as will be explained later underOperation. This relay includes the windings I11 and I18 and'the contactmembers I18, I and SI. Energization of winding I11. willv cause'therelay contact members to assume theright-hand position as viewed in thedrawing andener gization of winding I18 will cause themtoassume theleft-hand position. This being; a polarized relay, energization ofeitherwinding need only to be momentary, the relay contact membersremaining in the selected position until the other winding is energized.

The relay I21 includes the contact members I26 and H35, alreadymentioned, and the contact members I82, I53 and I84. The contact membersI25 and I65are front and back contact members, that. is, one contact ismade when the winding of the relay is energized and.- arrother is madewhen-the winding is not energized.- The contact members I82, I83 and I84are front contact members, that is, there are actuated from adropped-out or open position, to, a, picked-up or closed position whenthe winding of the relay is energized.

The relay I31 includes the front contact mem bers I35 and I13, alreadymentioned, together with the front contact members I85, I86 and RelayI28 includes. a front contact member I88 and a back contact member I89.Relay I65 is identical in construction to relay I28 and'includes a frontcontact member I98 and a back contact member I9I. The term; back contactmember identifies a contact. member that. is

actuated from a dropped-out or closed position to a picked-up or openposition when the winding of the relay is energized.

This circuit checking equipment further includes a signal relay I52having the front contact members I93, I94 and I95 and the front and backcontact members I86 and I91.

The relay I84 is a two-winding relay, onewinding I98 of which isnormally energized to actuate the relay to a pick-up position by meansof a circuit apparent in the drawing controlled by a pneumaticallyoperated switch device I99. Switch device I99 hastwo contact members.280 and ZIJI which are spring-actuated 'toa closed position when fluidpressure in the switch is less than a preselected value, say fivepounds/per square inch, and actuated to open position by fluid pressureexceeding such. pressure.

A second winding 202 of relay I84 is included in a circuit extendingfromrtherelease control wire 63 byway of lead I5I, wire I49, a wire 203,contact member 2iil of switch I99, wire 204, winding 282, and wire 285to wire II2, then by way of switch III, fuse IID, lead I08 and wire 15to the negative side of the battery. The current flow through winding282 produces a magnetic effect in opposition to that of winding I98 soas to cause the relay to assume a deenergized or dropped-out positionwhen the windings/I918v and 20 21 are simultaneously energized. Thisoperation occurs at the initiation of a. brake application when. therelease contacts. of thethe front and back contact members 201, 20.8,

and 209.

Relays 192 and 104, through their contact members 196, 191, 201 and 208control signals 210, 211 and 212 on the equipment box, together with andin parallel with signals 213, 214 and 215 in the operators cab orcompartment as will later be explained.

The switch 132 comprises the heretofore mentioned switch contacts 134,131, 111 and 169 which are normally closed by spring forces togetherwith a normally open contact member 216, said contact member beingspring returned to the open position when manual forces are moved fromthe switch. The handle of this switch is operative to a position oneside of a normal position for operation of the spring closed contactmembers 134, 131, 111 and 169 to the open position. The handle isoperative to a position at the opposite side of the normal position forclosing the contact member 216 against spring force.

A pneumatic switch device 211 includes normally closed contact members218 in parallel with the contact member 195 of the signal relay 192 in acircuit including the magnet valve device 4 and the switch device 91.The pneumatic switch is controlled by fluid pressure in the straight-aircontrol pipe 11 and is arranged to open the contact member 218 so longas a pressure exceeding a predetermined low pressure of say five poundsper square inch is established in the control pipe 1 1.

Supply battery voltage is provided in this circuit checking apparatusfrom the positive battery wire 61 by way of lead 219, binding post 220,fuse 221 and switch 222 to wire 223. To avoid needless repetition,hereinafter, the wire 223 will be referred to as the battery supply wireand circuits traced by reference thereto.

In like manner the Wire 1 12 being connected to the negative side of thebattery 60 by wire 15, lead 108, binding post 109, fuse 118 and switch 11 1 will hereinafter be referred to as the battery return wire andcircuits will be traced with reference thereto.

Operation In conditioning the circuit checking apparatus for operation,the operator first balances the bridge arrangements by moving thecontrol handle of switch 132 into the position for opening the contactmembers 134, 131, 111 and 169. The circuits forshort-circuiting thethird and fourth branches of the two bridge arrangements are thus openedby the opening of the contact members 134 and 111. The opening ofcontact members 131 and 169 opens the circuits by-passing the meters 129and 161. The contact arms 120 and 159 are manually adjusted on theresistors 119 and 158 until a zero reading of the meters 129 and 161 isgiven. A balanced condition of the bridge arrangement is thus obtained,in which condition the resistance of the variable resistor in the fourthbranch of the bridge is equal to the resistance of the train brakecontrol circuit inclinded in the third branch of the bridge arrangement.The position of the contact arm on the variable resistor should indicateon the escutcheon plate the number of brake control units in the trainattached to the locomotive. If this indication does not agree with thenumber of cars in the train, a faulty circuit condition is thusindicated. For example, if both contact arms 120 and 159 are positionedto indicate eight cars in the train when in reality there are ten cars.an indication is given that the train line connector between cars eightand nine is separated or that the return circuit 15 is open between carseight and nine. If one of the contact arms is positioned to indicateeight cars and the other contact arm positioned to indicate ten cars inthe train, the indication is that the control circuit included in thebridge arrangement giving the eight car indication is open between carseight and nine.

A grounded control circuit, or a short-circuit between the control wireand the return wire is indicated by an indication of more cars in thetrain than there actually are and by an inability to balance the bridgesby contact arm adjustment on its respective resistor.

With the bridge arrangements balanced, the brake valve handle 9 inrelease position, and the selector 10 in straight-air operationposition, the contact members 200 and 201 of the switch device 199 andcontact member 218 of the switch device 211 are closed, responsive tothe atmospheric pressure values in the straight-air pipe 50 and thestraight-air control pipe 11. A circuit is thereby coupled from thebattery supply wire 223 by Way of wire 224, contact member 200, wire225, winding 198 of the relay 104 and wire 226 to the battery returnwire 112, energizing the winding 198 and actuating the relay to apickedup condition in which the front contact members 103, 148, 206 areclosed and front and back contact member 208 and 209 are in their upperclosed positions. A circuit is thus established from the battery supplywire 223 by way of the contact member 209, wire 221, to wire 228, thencethrough resistors 114 and 115 to the junction 163 of the first andsecond branches of bridge arrangement 93 and through resistors 138 and139 to the junction 124 of the bridge arrangement 92. Parallel circuitsare now completed by first and fourth branches and second and thirdbranches of each bridge arrangement to the respective junctions 114 and153 which are connected to the battery return wire 1 12 by wires 113 and152.

A circuit for charging the condenser 233 is also completed from the wire228 via wire 229, resistor 230, wire 231, contact member 180 in itsleft-hand position and wire 232 to condenser 233, the opposite side ofwhich is connected to the battery return wire 112 by wire 234.

The bridge arrangements having been balanced, the relays 128 and 166 aredeenergized. A circuit is now complete for energizing relay 131 via theback contact members 189 and 191, wire 235, contact member 119 in itsleft-hand position, the winding of relay 131 and wire 234 for actuatingthe relay 131 to a picked-up condition in which the front contactmembers 136, 113, 185, 186 and 181 are in closed position. The fourthbranch of bridge arrangement 92 is short-circuited via closed contactmember 136, wire closed contact member 134 to junction 114, and thefourth branch of bridge arrangement 93 is shortcircuited via closedcontact member 113, wire 112, closed contact member 111 to junction 153.

By reason of the reduced resistance of the short-circuit path ascompared to the third branch of the bridge arrangements, current willflow from the junction of the second and third branches by wire 133,contact member 131, wire 130, the Winding of relay 128 and theshort-circuit path to the battery return wire to actuate relay 128 to apicked-up condition. The relay 166 of bridge 93 is energized by asimilar circuit. With relays 128 and 166 simultaneously energized, theback contact members 189 and 191 are effective in, their open positionto interrupt the circuit previously tracedior energizing the Winding ofthe relay I31 and. the front contact members I88, I90 and I85 areeffectivewhen in closed position to establish a circuit for energizingthe upper winding I11 of the relay I16 to efiect movement of the relacontact member's. I19, moi-and I8I from their left-hand position. totheir righthand position as'seen inthe drawing Movement of the contactmember. I80,- of relay I16. from the left-hand positionto the right-handposition first opens the circuit from. the battery supply wire and wire23I for charging the con-.

denser 233 and then closes a circuit, over wire 231 for charging thecondenser 23.8. Relay I31 is not dropped out instantly when contactmember I19 of relay I16. shifts to, its right-hand position but is heldpicked-up for an interval of time by discharge of current from condenser233.

the contact member 209, wire 2.21, the. contact I81 of relay I31 andcontact member I.8,I. of re-. lay I16 to-energize a wire 240 leadingtothe contact members H6. and I93.

After the condenser 233 is discharged and; no longer maintains the relaI31. in a piokedup position, therelay is restored to the dropped-outposition opening the front contact members I36, I13, I85, I88 and I81.Contact member I811. thus acts to open the circuit for energizing thewire 240. With the contact members I36 and I13 open, the circuit forshort'circuiting. the fourth branch'of each of thebridges 92 and 93. isopen andj the bridges, are returned to their normal condition. If thetrain circuit, has not changed inits resistanc e, the bridges willremain balanced and the relays I28 and [66, will becOme deener-. gized,thus opening theiront contact members I88 and I90 and closing the backvcontact mem bers I89 and I9I.

The closing of back contact members I89. and IBInow closes a circuitfrom the supply wire 22!; over Wire 229, resistor 2.3.0, contact membersI89 and HI over wire 235 and the contact member I19 in itsright-handl'position, the winding ofrelay I21 to the battery return wireby way of wire 234. The relay I21 is thus energized, and actuated to thepicked-up position in which the contact members I26, I65, I 82, I83 andI84 are closed. The closing of contact member I26 completes a. lowresistance substitute circuit fromv a junction of :the. second. andthird branches, of the bridge arrangement 92 over the front. contactmember I26], wire I35, contact member I34to the junction point I,I4 forthe thirdbranch of the bridge arrangement 92 whichis opened, by theopen.- i'ngof the back contact. member I26; The third branchof thebridge arrangement 931s. also substituted'for by a-similar-lowresistancecircuit. The relays I 28, and I66 are now. energized'byreasonof flow of current from the junction of the first andfourthbranches of the bridge over the relay winding and the shortcircuit path to the battery return wire through the relay winding in. adirection opposite to, the current flow in 18 the windings, as a resultof a short-circuiting of the fourth branches of a bridge. The closureofcontact member I 82 by the energization of relay I21 prepares a circuitwhich is completed, by the closing of contact members I88 and I90,fromthe wire 223, and, resistor 230over the. lower winding: I18. ofrelay I118 to the battery return wire 234 torenergizing. the. relay I16and effecting movement of the contact, members I19, I and I 8| fromtheir respective right-hand positions back to their respective left-handpositions.

A circuit is now, completed from the. wire 228 over the closed. frontcontact. member I84. of relay I21, the contact member I8I in its.lefthand position for momentarily energizing, the. Wire 240. The shiftof the. contact member I180 from its right-hand to its left-handposition removes the. battery supply voltage from. the condenser 238 andthe, closed contact member I83.

supplies the. charge. of the condenser 238 over a.

. ergized or dropped out, thus opening front contact members I82, I83and, I84 and shiftingcon-- tact members. I26- and- I65-to their lowerclosed positions. The. fourth branches of the bridge arrangements 92 and93: are restored in the bridge arrangementandif the bridge balanceremains.- truethe relays I28 and I661 become deenergized. to condition,the bridge circuit for another cycle of operation. I

From the. above-description it can. be seen the 1 continuous operation.of the bridge circuit, and.

the relays I28, I86}, I31, I21 and. I16 will be effect-v ed.s0 long. asthe, bridge circuits remain. balanced. The cycle of operation occurs ata selectedf-re. quency, such as thirty timesv per. minute. Sincetyvoimpuses of current per. cycle aretransmitted over wire 2401 to thecontact members 2I-6iand l93, this-meansthat, in the instance given?above,,the, frequency of current impulses; would; be of, the order of60. per minute.

With the equipment operating as just described, the operator willmovethe controllever of the switch I3,2.to position for closingthe,contact member 2I 6.. With the contact member. 216. closed, animpulse of current will. be supplied within two seconds of time. over,the. contact member 2'I6 and wire 242, over the closed con tact member206 and a resistor 243- for energiz ing the windingofrelay- I92 andeffecting; move ment of the contact members, I93; I96, 91, I34. and I95to the closed or upper closed positions. The impulse of current forenergizing the relay, I92; is also supplied to the condenser 2:44 forcharging the condenser. With the; condenser 244. charged to the batteryvoltage, i'ti will'by reason of a closed circuit hold'the relay I82;energized for slightly morethan a two second period until anotherimpulse of current is provided over. the wire 24.0.. With the relayI92'energized and the front contact member I93: closed, it: will: nolonger be necessary to holdicontactmember 2 It6.of" switch I32 in closedposition. Any. impulse of current provided on wire- 240will be suppliedby way. of contact member I93, wire 242', a closed contact member 206and the resistor 243 for energizing the winding of relay I92 andrechargingthe condenser 244. It can thus be seen that so long as theimpulses are supplied to-the wire 240 at the prescribed interval of timebefore the condenser 244 becomes discharged the relay I92wi1l 19 bemaintained energized and consequently picked- While the relay I92 ismaintained picked-up, a circuit for energizing the signal 2 I iscompleted from the battery supply wire 223 over resistor 245, contactmembers I95 and 20! in their upper closed positions, the signal 2 If) tothe battery return wire I I2. At the same time, battery voltage from thesupply wire 223 is supplied over the resistor 256, the contact membersI91 and 268 in their upper closed positions, to energize the signal 2I3in the cab of the locomotive. The signals Eli) and 2I3 are energizeduntil a faulty condition of the bridge circuit is encountered, or untila brake application is made.

Should a change in resistance of either or all control circuits arise,such changes being caused by failure of magnet windings, couplers,Wires, by loss of or addition of cars, short or grounded circuits, etc.,the bridge arrangement will not balance when the short circuits of thebridge branch is removed. In such case, the detector relay in therespective bridge arrangement will not drop out. The circuit overcontact members I89, I9I, wire 235, contact member I'I9, to energize theselected relay I31 or IT! is thus not made. The coding operation ofrelays I28, I66, I31, I27 and I16 is thereby interrupted and the impulsefor recharging the condenser 2% fails, thus the relay I92 becomesdeenergized. With relay I92 thus deenergized the back contact mem bersW6 and I9? are closed. and the front contact members are open. The backcontact member I98 in closed position is effective to complete a circuitfrom the supply wire 223 by way of the resistor 245 for energizing thedanger signal 2I2. At the same time battery voltage is supplied overresistor 246, back contact member I9! for energizing the danger signal2I5 in the locomotive cab. As has been explained, the operator can, byoperating the switch I32 to open the normally closed contact members andby adjustment of the contactor arms I20 and I59 determine the locationand nature of the fault in the control circuit.

If during the time the clear signals 2Ii and 2I3 are energized, theoperator desires to make a straight-air brake application the releasewire 63 will first be energized, as has been explained, and circuit willbe provided for energizing the lower winding 262 of relay I04 by way ofthe lead II, wires I49 and 253, the switch contact member ZIlI, of theswitch I99, wire 204, the lower winding 232 of the relay I34, and wire255 to the battery return wire II2. This energization of winding 202will effect movement of the relay 564 to the dropped out position inwhich the front contact members are opened and the back contact members231 and 288 and 2G3 are shifted to their lower closed positions. Theback contact member 239 closes a circuit from the battery supply wire223, by Way of the back contact member 253, the front contact membersI94, resistor 243 for maintaining the relay I92 energized from thebattery supply voltage. At the same time, battery voltage is providedfrom the supply wire 223, resistor 245, the front contact member I33,the back contact member 201 to energize the signal 2 and over resistor246, front contact member I92, back contact member 258 for energizingthe signal 2M on the locomotive cab. The signals 2 I I and 2 I4 whenenergized indicate that a brake application is effective throughout thetrain.

The front contact member I95 of the relay I92 is closed except during afault indication when the relay I92 is deenergized. The contact memberI95 is included in parallel with the contact members 2I8 oi thepneumatic switch 2I'I to control a circuit for energizing the magnetvalve de vice 4 (Fig. l). The switch device 2I'I is eilective todisengage or open the contact members 2I8 when a given fluid pressure isestablished in straight-air control pipe I I. It can thus be seen thatif a fault indication is given by the circuit checking appaartus thecontact member I95 will be open and if the operator attempts astraightair brake application, the switch contacts 2I8 will be opened toopen the circuit energizing the magnet valve device 4. The chamber 33 ofthe vent valve device 3 is thereby vented and, as previously described,an automatic brake application is effected by the venting of fluidpressure from the brake pipe by operation of the vent valve device.

It should be understood that while my invention has been disclosedspecifically in connection with two control circuits, it is not limitedin its operation to any particular number of control circuits. In otherwords, it may be employed in connection with a single control circuit ormore than two control circuits. If my invention is employed inconnection with a single control circuit, only one corresponding bridgearrangement and one detector relay is required to control the operationof the coding relays. If my invention is employed in connection withmore than two control circuits, a corresponding number of bridgearrangements and detector relays will be employed with the contactmembers of the detector relays connected in series relationship forcontrol of the coding relays.

Having now described my invention, what I claim as new and desire tosecure by Letters Patent, is:

1. For use with an electric brake control system for a train of carswhich system includes an electric control circuit and anelectro-responsive control unit on each car operating on said circuit, afidelity checking apparatus comprising a Wheatstone bridge arrangementhaving as one branch thereof the control circuit and having a secondbranch including an adjustable resistor unit for effecting a balancedcondition of the bridge arrangement, means associated with said resistorunit calibrated to indicate the number of electro-responsive controlunits effectively operating on the control circuit, said resistor unitand calibrated means cooperating to verify the integrity of the controlcircuit so long as the indication given corresponds to the actual numberof cars in the train and to indicate the location of a fault when thereis variance between the indication and the actual number of cars.

2. For use with an electric brake control system for a train of carswhich system includes an electric control circuit and anelectro-responsive control unit on each car operating on said circuit, afidelity checking apparatus comprising a Wheatstone bridge arrangementhaving as one branch thereof the control circuit and having a secondbranch including an adjustable resistor unit for effecting a balancedcondition of the bridge arrangement, said resistor unit being calibratedto indicate the number of electro-responsive control units effectivelyoperating on the control circuit and effective to verify the integrityof the control circuit so long as the indication given corresponds tothe actual number of cars in the train and to indicate the location of afault when there is variance between the indication and the actualnumber of cars, relay means responsive to the balanced condition of thebridge arrangement to produce an intentional unbalanced conditionthereof and responsive to the intentional unbalanced condition .of thebridge arrangement to restore the balanced condition thereof so long asno fault exists on said control circuit, and means responsive to thecontinued operation of the said relay means to repeatedly effect thebalanced and unbalanced conditions of said bridge arrangement insuccession for indicating the integrity of the brake control circuit.

3. For use with anelectric brake control system for a train of carswhich system includes an application control circuit having anelectro-responsive application control unit on each car of the trainoperating thereon and a release control circuit having anelectro-responsiverelease control unit on each car operating thereon,apparatus comprising a Wheatstone bridge arrangement including theapplication control circuit as a branch thereof and another Wheatstonebridge arrangement including the release control circuit as a branchthereof, each bridge arrangement further including as a second branchthereof a resistor unit adjustable to conform to the resistance of thecorresponding control circuit to produce a balanced condition of thatbridge arrangement, said resistor unit being calibrated to indicate thenumber of control units operating effectively on the correspondingcircuit and effective to verify the integrity of the control circuit solong as, the indication as to the number of control units corresponds tothe actual number of cars in the train and to indicate the location of afault when there is variance between the indication and the actualnumber of cars, relay means operative, to simultaneously vary theresistance of said one branch of each bridge arrangement and then thesaid second branch of each bridge arrangement for periodically producingan intentional unbalanced condition of each bridge arrangement, aplurality of detector means each associated with a corresponding bridgearrangement and having a normal position responsively to the balancedcondition of the corresponding bridge arrangement and actuated to adifferent position responsively to the unbalanced condition of thecorresponding bridge arrangement, said plurality of detector means beingeffective so long as they operate in synchronism for causing said relaymeans to operate in repeated cycles to effect the unbalanced andbalanced conditions of the bridge arrangements,

said relay means being effective, so long as it continues to operate, toproduce a coded signal having at least a certain frequency, and meansresponsive to said coded signal of a certain frequency for indicatingthe integrity of said plurality of control circuits.

4. Apparatus for checking and indicating the integrity of an electriccontrol circuit, said apparatus comprising a Wheatstone bridgearrangement having the control circuit to be checked as a branch thereofand having a resistor unit constituting another branch of said bridgearrangement capable of adjustment to conform to the resistance of saidcontrol circuit whereby to balance said bridge arrangement, meanseffective, once the bridge arrangement is balanced, to compensate forvariations in the resistance of the control circuit due to changes inatmospheric temperature to prevent undesired unbalance of the bridgearrangement due to temperature changes, means responsive to thebalancedcondition of the bridge arrangement to produce an intentionalunbalanced. condition thereof and responsive to the intentionalunbalanced condition of the bridge arrangement to restore the balancedcondition thereof so long as no fault on said control circuit occurs,and means responsive to the continued operation of the last said meansto repeatedly effect the balanced and unbalanced condition of saidbridge arrangement in succession for'indicating the integrity of saidcontrol circuit.

5. Apparatus for checking and indicating the integrity of an electriccontrol circuit, said apparatus comprising a Wheatstone bridgearrangement including as one branch thereof a fixed resistor, a secondbranch including a temperature compensating resistor, a third branchincluding said control circuit and a fourth branch including a resistorunit adjustable to conform to the resistance of said third branchwhereby to effect a balanced condition of said bridge arrangement, meansresponsive to the balanced condition of the bridge'arrangement toproduce an intentional unbalanced condition thereof and responsive tothe intentional unbalanced condition of the bridge to restore thebalanced condition thereof so long as no fault occurs on said controlcircuit, said temperature compensating resistor being subject toatmospheric temperature and having an electrical characteristic suchthatit compensates for changes in the control circuit resistance due toatmospheric temperature changes in a manner toprevent undesiredunbalance of the bridge arrangement, and means responsive to thecontinued operation of the said means responsive to the balanced andunbalanced conditions of the bridge arrangement for indicating theintegrity of the control circuit.

6. Apparatus for indicating the integrity or lack of integrity of anelectric control circuit, said apparatus comprising a Wheatstone'bridgearrangement having the control circuit to be checked as a branch thereofand having a resistor unit constituting another branch thereof, whichresistor unit is adjustable to conform to the resistance of said controlcircuit so as to produce a balanced condition of said bridgearrangement, a circuit'for applying an operating voltage to the supplyterminals of said bridge arrangement, means effective automatically inaccordance with the adjustment of said resistor unit for reducing theoperating voltage applied to said bridge arrangement, means responsiveto a balanced condition of the bridge arrangement to produce anintentional unbalanced condition thereof and responsive to theunbalanced condition to restore the balanced condition of the bridgearrangement so long as no fault exists on said. control circuit, andmeans responsive to the continued operation of the last said means torepeatedly effect the successive balanced and unbalanced conditions ofthe said bridge arrangement for indicating the integrity of said controlcircuit.

7. Apparatus for indicating the integrity or lack of integrity of anelectric control circuit, said apparatus comprising a Wheatstone bridgearrangement having the control circuit to be checked as a branch thereofand having a variable resistor unit constituting another branch thereof,which resistor is adjustable to conform to the resistance of saidcontrol circuit so as to produce a balanced condition of said bridgearrangement, a circuit for applying an operating voltage to the supplyterminals of said bridge arrangement, a resistor in said circuit, ashunting switch efiective automatically in response to adjustment ofsaid adjustable resistor for unshunting said resistor to within acertain range to efiect reduction of the voltage applied to said bridgearrangement, and effective over the remaining range of adjustment of theadjustable resistor to shunt the said resistor, means responsive to abalanced condition of the bridge arrangement to produce an intentionalunbalanced condition thereof and responsive to the unbalanced conditionto restore the balanced condition of the bridge arrangement so long asno fault exists on said control circuit, and means responsive to thecontinued operation of the last said means to repeatedly effect thebalanced and unbalanced conditions of the said bridge arrangement forindicating the integrity of said control circuit.

8. Apparatus for checking and indicating the integrity of an electriccontrol circuit, said apparatus comprising a Wheatstone bridgearrangement including the control circuit to be checked as a branchthereof and having as a second branch thereof a resistor unit capable ofadjustment to conform to the resistance of said control circuit tobalance the bridge arrangement, resistance changing means foralternately varying and restoring the resistance of first one and thenthe other of said branches so long as no fault occurs in said controlcircuit, an indicating means for indicating a balanced or unbalancedcondition of the bridge arrangement when adjusting said resistor, acircuit for normally shunting said indicating means, switch meansmanually operable to prevent operation of said resistance changing meansand for opening said shunting circuit when initially balancing saidbridge arrangement, and means responsive to the continued operation ofsaid resistance changing means for indicating the integrity of saidcontrol circuit.

9. For use in connection with an electric control circuit adapted to beenergized and deenergized, apparatus for checking and signaling theintegrity or lack of integrity of an electric circuit, and meanseffective upon deenergization of said electric control circuit forconnecting said apparatus to said electric control circuit and effectiveupon energization of said control circuit to disconnect said apparatusfrom said control circuit.

10. For use with an electric control circuit of an electro-pneumaticbrake equipment wherein the said control circuit is energized ordeenerr:

gized for applying and releasing the brakes, apparatus operative tocheck and indicate the integrity or lack of integrity of an electriccircuit, and means eifective upon deenergization of the said controlcircuit to connect said apparatus to said control circuit and initiateoperation of said apparatus to indicate the integrity or lack ofintegrity of said control circuit, and effective upon energization ofsaid control circuit for disconnecting said apparatus from said controlcircuit and terminating operation thereof.

11. For use in connection with an electrically controlled brake controlequipment having electric control circuits adapted to be energized ordeenergized for controlling the brake release and the brake application,apparatus adapted to be connected to the electriccontrol circuits ofsaid brake equipment for checking and indicating the integrity or lackof integrity of said control circuits, and relay means operativelyeffective upon (ill 24 a brake release for connecting said apparatus tosaid control circuits and operatively effective upon initiation of abrake application for disconnecting said apparatus from said controlcircuits.

12. For use in connection with an electrically controlled brake controlequipment having electric control circuits adapted to be energized ordeenergized for controlling the brake operation, apparatus adapted to beconnected to the electric control circuits of said brake equipment forchecking and indicating the integrity or lack of integrity of saidcontrol circuits, relay means responsive to a brake release operationfor connecting said apparatus to said control circuits and responsive toinitiation of a brake application operation for disconnecting saidapparatus from said control circuits, and means controlled by said relaymeans and operative when said relay means disconnects said apparatusfrom said control circuits for indicating a brake application.

13. For use in connection with an electropneumatic brake control systemfor a train of cars which brake system includes a plurality oi controlcircuits extending from car to car throughout the train and beingadapted to be selectively energized or deenergized for controlling theapplication and release of the brakes on the train, apparatus forchecking the integrity of the control circuits of the brake systemcomprising a first relay adapted to be maintained in one position solong as the integrity of said control circuits is not impaired andoperated to a second position upon impairment of the integrity of saidcircuits, a second relay, means for effecting actuation of said secondrelay to one position so long as the control circuits are deenergizedand eiiective upon energization of said control circuits to cause saidsecond relay to be operated to a second position, and three signaldevices, one of which is energized under the joint control of the saidfirst relay in its said one position and said second relay in its saidone position to indicate the non-impairment of integrity of said controlcircuits, the second of which is energized under the joint control ofsaid first relay in its said one position and said second relay in itssaid second position to indicate the energization of the controlcircuits, and the third of which is energized under the sole control ofsaid first relay in its said second position to indicate the impairmentof integrity of said control circuits.

14. For use in connection with an electropneumatic train brake controlsystem including a plurality of control circuits extending from car tocar throughout the train and adapted to be operatively energized ordeenergized to control the application and release of the brakes,apparatus for signaling the integrity of the control circuits, saidapparatus comprising means operative to provide a certain coded signalonly so long as no fault on the control circuits exists, a tuned relaycontrolled responsively to the said certain coded signal and maintainedin one certain position only so long as the said certain coded signalcontinues, a second relay, means controlling said second relay in amanner such that it is operative from one position to a second positioninstantly upon operative energization of at least one of the controlcircuits and restored to its said one position upon operativedeenergization of said circuit, means providin a circuit for maintainingsaid tuned relay in its said one certain position upon movement of saidsecond relay to its said second position, independently of continuanceof the said certain coded signal, REFERENCES CITED and two signaldevices under the joint control of The following references are ofrecord in the said tuned relay and said second relay, one of file ofthis patent;

said signal devices being energized selectively under the control ofsaid second relay while 5 UNITED STATES PATENTS in its said one positionto indicate the integrity Number Name Date condition of the controlcircuits, and the other 1,765,475 White June 24, 1930 of said signaldevices being selectively energized 2,052,190 Miller et a1 Aug. 25, 1936under the control of said second relay in its said 2,055,563 Sorensen eta1. Sept. 19 second position to indicate a brake applied con- 102,091,007 McCune Aug. 24, 1937 dition of the brake system. 2,276,706Sorensen Mar. 17, 1942 CLAUDE M. HINES. 2,478,000 Miller Aug. 2, 1949

